Directed modification of glucosamine synthase mutant and application thereof

Abstract

The present invention discloses a directionally modified glucosamine synthase mutant and its application. The amino acid sequence of the glucosamine synthase mutant is as shown in sequence list SEQ ID No. 1, and the nucleotide sequence is as shown in sequence list SEQ ID No. 2. The genetic engineering bacteria of glucosamine synthase is successfully constructed. In order to improve the tolerance of recombinant bacteria against glucosamine, the glucosamine synthase is directionally modified. A glucosamine synthase mutant is selected from the mutant library via high-throughput screening method, the amino acid changes in the mutant induces the spatial conformational change in the enzyme, so as enlarged the region where the enzyme and substrate combines, therefor the combination efficiency of the enzyme and the substrate is increased. The glucosamine synthase of the present invention has various advantages, such as rich in raw material of glucose, and a convenient subsequent extraction.

What is claimed is: 
     
       1. A directionally modified glucosamine synthase mutant, having the amino acid sequence of SEQ ID No: 1. 
     
     
       2. The directionally modified glucosamine synthase mutant according to  claim 1 , wherein a gene encoding the directionally modified glucosamine synthase mutant have the nucleotide sequence of SEQ ID No: 2. 
     
     
       3. A method for biosynthesizing a glucosamine by using a directionally modified glucosamine synthase mutant, comprising the following step: converting glucosamine of a fermentation system into acetylated glucosamine through co-expressing the directionally modified glucosamine synthase mutant and a glucosamine acetyltransferase; wherein the directionally modified glucosamine synthase mutant has the amino acid sequence of SEQ ID No: 1.